James, As far as I can tell, the digital input signal (stimulus) you mentioned has nothing to do with what David and Terry are talking about. That digital signal is purely an indication for the analog signal (whether it is governed by [Ramp] or the V-t tables, doesn't matter) to begin its course. This is basically t=0 for the transition. The transition amplitude and slope is defined by the reference voltages of the I-V tables and [Ramp] or V-t tables. This is all analog. There are models out there which try to make this "model" as ideal as possible, giving it really fast edge rates and very strong I-V current relationships, so that the block that follows could be used for "wave shaping" and "impedance definition". I like to call this approach as the "Glorified Thevenin" model, in which the IBIS analog model acts as the ideal source and the next block (often times an S-parameter model) is the Thevenin impedance. But I don't see any relationship in this and the "digital" stimulus that goes into the legacy IBIS models. Thanks, Arpad ===================================================================== From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of James Zhou Sent: Monday, March 12, 2012 4:11 PM To: Terry.Chen@xxxxxxxxxx; DBanas@xxxxxxxxxx; 'IBIS-ATM' Subject: [ibis-macro] Re: Question on dividing up the Tx behavior between the AMI and analog portions of the model Hi David and Terry, Both of your emails mentioned "analog IBIS model" and "IBIS-analog portion" represented by [Ramp] and/or [Rising/Falling Waveform] keywords in IBIS file. However, these "analog" IBIS models only take digital input signals, as stated in IBIS Specification 5.0, page 71-72 and section 6b. The output of the "analog" IBIS model is not capable of tracking the amplitude changes in the input (other than a rise/fall transition). It would not make sense to feed the Tx AMI output to such digital inputs based on IBIS Specification 5.0. If this approach of using [Ramp] and/or [Rising/falling Waveform] keywords to represent "analog IBIS model" is adopted by IBIS AMI flow, some clarification is needed on how to interpret and implement it. Regards, James Zhou QLogic Corp. From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]<mailto:[mailto:ibis-macro-bounce@xxxxxxxxxxxxx]> On Behalf Of Chen, Terry Sent: Thursday, March 08, 2012 10:33 AM To: DBanas@xxxxxxxxxx<mailto:DBanas@xxxxxxxxxx>; 'IBIS-ATM' Subject: [ibis-macro] Re: Question on dividing up the Tx behavior between the AMI and analog portions of the model Hi David, Actually I am interested in other's response to this question as well... But, for the TX Driver I am currently modeling, I am doing exactly what you have prescribed and using the IBIS-analog portion as effectively an ideal step function (by setting my ramp with extremely high rise/fall dv/dt) and letting the step response filter inside my AMI model to shape my output waveform. Now, I am not sure if this is the "right" or "ideal" way to do it, but I am getting a reasonably good correlation in my Re-driver model with the actual lab measurements (the max jitter mismatch is < 8ps). I hope this is at least an useful data point for you. Regards, Terry From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]<mailto:[mailto:ibis-macro-bounce@xxxxxxxxxxxxx]> On Behalf Of David Banas Sent: Thursday, March 08, 2012 1:15 PM To: 'IBIS-ATM' Subject: [ibis-macro] Question on dividing up the Tx behavior between the AMI and analog portions of the model Hi all, Is it customary to split up the Tx behavior, such that the FFE is modeled in the AMI model and the pulse shaper in the analog model? Or, is there a different dividing line that has been identified as "best practice". (Or, am I completely off in the weeds?) The context for this question: I just managed to get good correlation between our latest Tx AMI model and the HSPICE model. And then I realized that, having dumped all of the behavior into the AMI model, I would need to put an ideal step function into the V-T curves of the analog IBIS model. And I wasn't sure that would be a good idea. (I'm guessing that that would reek havoc in most simulators; is that correct?) Thanks, David Banas Sr. Member Technical Staff Altera<http://www.altera.com/> +1-408-544-7667 - desk Did you know Altera offers over 150 free online technical training courses<http://www.altera.com/servlets/searchcourse?coursetype=Online&WT.mc_id=t9_ot_mi_mi_tx_a_311>? Take one today! ________________________________ Confidentiality Notice. This message may contain information that is confidential or otherwise protected from disclosure. If you are not the intended recipient, you are hereby notified that any use, disclosure, dissemination, distribution, or copying of this message, or any attachments, is strictly prohibited. If you have received this message in error, please advise the sender by reply e-mail, and delete the message and any attachments. 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